Re: NEC-LIST: Helix in NEC-2

On Tue, 13 Jan 2004 06:02:04 -0800 (PST)
"D. B. Miron" <dbmiron_at_paulbunyan.net> wrote:

> Good day Roy,
>
> Also, what other undocumented
> commands are there? I've written C++ code to generate coils
> as part of my wire-list-generating programs. Mine start and
> finish on the z axis, winding out to the specified cylinder
> radius in a half-turn. What does the GH command do?

Below is the documentation of the GH command - it is hardly an
undocumented command! I have it as part of and old (fortran) NEC-2
version...

John

Basic structures:

# Structure Geometry Input

    * Wire Arc Specification(GA)
    * End Geometry Input (GE)
    * Read NGF File (GF)
    * Helix - Spiral Specification (GH)
    * Coordinate Transformation (GM)
    * Generate Cylindrical Structure(GR)
    * Scale Structure Dimensions (GS)
    * Wire Specification (GW)
    * Reflection in Coordinate Planes (GX)
    * Surface Patch (SP)
    * Multiple Patch Surface (SM)
    * Examples of Structure Geometry Data

The GH construct:

Card:

         Cols Parameter
        ----------------------
         1- 2 GH
         3- 5 I1 - ITG
         6-10 I2 - NS
        11-20 F1 - S
        21-30 F2 - HL
        31-40 F3 - A1
        41-50 F4 - B1
        51-60 F5 - A2
        61-70 F6 - B2
        71-80 F7 - RAD

Parameters:

    Integers

           ITG (11) - Tag number assigned to all segments of the helix or
                        spiral.
           NS (12) - Number of segments into which the helix or spiral
                        will be divided.

    Floating Point

           S (F1) - Spacing between turns.
           HL (F2) - Total length of the helix.
           A1 (F3) - Radius in x at z = 0.
           B1 (F4) - Radius in y at z = 0.
           A2 (F5) - Radius in x at z = HL.
           B2 (F6) - Radius in y at z = HL.
           RAD (F7) - Radius of wire.

    * Notes: Structure will be a helix if A2 = A1 and HL > 0.
    * Structure will be a spiral if A2 = A1 and HL = 0.
          o Unless it has been fixed in the codes in circulation, the use
of HL=0 for a flat spiral will result in division by zero in NEC-2. GH was
a non-official addition to NEC-2 * HL negative gives a left-handed
helix. * HL positive gives a right-handed helix.

Note JC: at least nec2dxs uses S to indicate handedness

    * S positive gives a right-handed helix
    * S negative gives a left-handed helix

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